Most SARS-CoV-2 infections occurred outside workplace

Workplace exposure was not a significant source of Covid-19 transmission among health care workers, according to a cross-sectional study that involved close to 25,000 front-line employees of four health systems in geographically distinct regions of the U.S. and conducted at different stages of the pandemic.

The strongest risk factors associated with SARS-CoV-2 seropositivity among the health care workers were exposure outside the workplace and living in a zip code with higher Covid-19 incidence. Working as a nurse, working in a hospital emergency department, and working among patients with Covid-19 were not found to be significant sources of seropositivity in the study, published online in JAMA Network Open.

The study results suggest that for health care workers, the risk for SARS-CoV-2 infection from community exposure may exceed the risk from patient exposure, wrote researcher Jesse Jacob, MD, of Emory University School of Medicine, Atlanta, and colleagues.

“These findings provide reassurance that current infection prevention practices in similar health care systems are effective and that the largest risk may be conferred from community-based exposures,” they wrote.

The researchers noted that their study was designed to address important unanswered questions about the Covid-19 risk faced by health care workers during the pandemic.

“It remains unclear whether certain job functions or specific workplace activities, including care for individuals with known and unknown SARS-CoV-2 positivity, increase the risk of SARS-CoV-2 infection,” they wrote. “Furthermore, it is still unknown whether the association of individual- and job-related characteristics and risk of SARS-CoV-2 infection are consistent across health care systems and over time.”

The study included 24,749 health care personnel (HCP) from four large health care systems enrolled in the CDC’s Prevention Epicenters Program (Emory Healthcare, Atlanta; Johns Hopkins Medicine and The University of Maryland Medical System, Baltimore; and Rush University System, Chicago).

All four sites shared de-identified data sets, including previously collected serology results, questionnaire results on community and workplace exposures at the time of serology, and 3-digit residential zip code prefix of health care workers participating in the study. Site-specific responses were mapped to a common metadata set, and residential weekly Covid-19 cumulative incidence was calculated from state-based Covid-19 case and census data. Specimen and survey data were collected from April 19-Aug. 30, 2020.

Model variables included demographic (age, race, sex, ethnicity), community (known Covid-19 contact, Covid-19 cumulative incidence by 3-digit zip code prefix), and health care (workplace, job role, Covid-19 patient contact) factors.

The main outcome was SARS-CoV-2 seropositivity and risk factors for seropositivity were estimated using a mixed-effects logistic regression model with a random intercept to account for clustering by site.

Over two-thirds (69.6%) of the HCP included in the study were younger than 50 years of age and more than three-quarters (78.2%) were female. Sixty-one percent were White, and 50.2% reported workplace contact with Covid-19 patients. More than a third (35.9%) of participants worked in the inpatient settings and 31.6% were nurses.

The cumulative incidence of Covid-19 per 10,000 in the community up to one week prior to serology testing ranged from 8.2 to 275.6, and 81.1% of the participating HCP reported no Covid-19 contact in the community.

A total of 1,080 HCP were seropositive for SARS-CoV-2 when tested (4.4%, 95% CI, 4.1%-4.6%). Testing volume peaked at different times at each site between April and August 2020.

Multivariable analysis revealed that community Covid-19 contact and community Covid-19 cumulative incidence were associated with seropositivity (community contact: adjusted odds ratio [aOR], 3.5; 95% CI, 2.9-4.1; community cumulative incidence: aOR, 1.8; 95% CI, 1.3-2.6).

None of the assessed workplace factors were associated with seropositivity, including nurse job role (aOR, 1.1; 95% CI, 0.9-1.3), working in the emergency department (aOR, 1.0; 95% CI, 0.8-1.3), or workplace contact with patients with COVID-19 (aOR, 1.1; 95% CI, 0.9-1.3).

“We found that the higher cumulative incidence of Covid-19 until the week prior to the antibody test, the higher the risk of the HCP being antibody positive,” the researchers wrote, adding that the finding “aligns well with the observed association that HCP who had contact with a person with Covid-19 in the community were more likely to be antibody positive.”

In a commentary published with the study, Shruti Gohil, MD, and Susan Huang, MD, of the University of California Irvine School of Medicine, Irvine, California, wrote that the study “represents one of the largest assessments of Covid-19 seroprevalence among HCP in the United States, and its findings highlight the protective effects of PPE and protocols in the hospital setting.”

“These findings help correct misperceptions that HCP remain at higher risk of communicable disease despite adequate [personal protective equipment] PPE and infection prevention protocols,” they wrote, adding that additional research is needed to better understand the optimization of health care worker adherence to established infection control protocols.

Study limitations cited by the researchers included the fact that participation in the research was voluntary, which might have skewed the results, and the fact that laboratory methods differed across sites. In addition, questionnaires were not standardized across sites and infection control practices also may have differed.

  1. Workplace exposure was not a significant source of Covid-19 transmission among health care workers in a cross-sectional study involving close to 25,000 front-line employees of 4 health systems.
  2. The strongest risk factors associated with SARS-CoV-2 seropositivity among the health care workers were exposure outside the workplace and living in a zip code with higher Covid-19 incidence.

Salynn Boyles, Contributing Writer, BreakingMED™

Funding for this research was provided by the CDC’s Prevention Epicentrers Program and the National Institute of Allergy and Infectious Disease.

The researchers reported no relevant disclosures related to this study. Commentary writers’ Gohil and Haung reported no disclosures.


Cat ID: 125

Topic ID: 79,125,254,930,728,932,730,933,125,190,926,192,927,151,928,925,934